Veterinary Services

Center for Epidemiology and Animal Health June 2015

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Mycoplasma ovipneumonia on 

U.S. Sheep Operations

Background

Respiratory disease in sheep and lambs is an 

important cause of economic losses on U.S. sheep 

operations. In 2009, 4.8 percent of nonpredator death 

losses in sheep and 12.6 percent of nonpredator death 

losses in lambs were attributed to respiratory diseases 

such as pneumonia or shipping fever (USDA, 2010). 

Other production losses caused by respiratory disease 

are more insidious but can be economically detrimental 

to sheep due to poor growth rates, decreased feedconversion efficiency, and increased labor and 

management costs (Alley, 1987). 

The bacterium Mycoplasma ovipneumonia is one of 

many common respiratory pathogens affecting domestic 

sheep and goats in the United States. It was first isolated 

in New Zealand in 1974 and has since been recovered 

from the respiratory tracts of healthy and symptomatic

sheep worldwide (Clark, 1974). Transmission occurs via 

aerosol spread and close contact with infected animals. 

M. ovipneumonia typically resides in an adult animal’s

nasal cavity, where it can spread easily to young lambs,

often causing transient, mild respiratory disease.

Subclinically infected sheep, when placed under stress 

due to shipping, weather, poor nutrition, or other factors, 

may develop acute pneumonia (Nicholas, 2008).

Alone, it is not normally highly pathogenic, but

M. ovipneumonia predisposes sheep to other respiratory 

infections by interfering with normal ciliary activity in the 

respiratory tract and by suppressing lymphocytes 

(Niang, 1998; Nicholas, 2008; Shahzad, 2010). In 1998, 

a combined infection of M. ovipneumonia and 

M. arginine was attributed to paroxysmal coughing,

leading to rectal prolapse and reduced weight gain in

lambs in the Midwestern United States (Niang, 1998). 

Combined M. ovipneumonia and Pasteruella hemolytica

infections are frequently found in lambs with chronic 

atypical pneumonia and low mortality rates. Economic 

losses can be high due to chronically unthrifty lambs. 

Mycoplasma ovipneumonia on 

U.S. sheep operations 

In 2011, the USDA’s National Animal Health 

Monitoring System conducted Sheep 2011, an in-depth

study of U.S. sheep operations conducted in 22 of the 

Nation’s major sheep-producing States. For the study,

these States were divided into three regions (see map).

Operations with more than one ewe met the study 

inclusion criterion; collectively, these operations 

represented 85.5 percent of the U.S. ewe inventory and 

70.1 percent of the U.S. farms with ewes (USDA, 2012). 

The Sheep 2011 study focused on sheep health and 

management and was the first study to estimate the 

national prevalence of M. ovipneumonia in U.S. sheep.

As part of the study, nasal swabs were collected from up 

to 10 adult ewes per flock on 453 operations in the 

13 participating States. These 10 swabs were then 

pooled and tested by PCR for M. ovipneumonia DNA 

fragments. Operations with PCR-positive pooled 

samples were considered positive. For operations in 

which pooled results were indeterminate or negative, 

individual ewe swabs were PCR tested. Operations were 

considered positive if they had one or more PCRpositive individual-animal samples. 

United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture
Of the pooled samples taken from the 453 

operations tested, 350 were initially positive for 

M. ovipneumonia and another 51 were positive after 

individual-animal nasal swabs were tested. Overall, 401 

operations (88.5 percent) were positive by PCR 

(table 1). Additionally, serum from up to 16 adult ewes 

per flock was tested for antibodies to M. ovipneumonia

using an ELISA test. Serum was collected from 4,073

ewes on 408 of the PCR-sampled operations from 

March 14 through June 30, 2011. At least one ewe was 

ELISA positive on 85.3 percent of these operations. 

Of the 4,073 individual samples tested, 1,199 

(29.4 percent) were seropositive using the ELISA. The 

mean within-flock seroprevalence in ELISA-positive 

flocks was 34.6 percent. 

Table 1. Number and percentage of operations 

and animals PCR and ELISA positive for 

M. ovipneumonia, by flock size

Number/Percent Operations

Flock Size (number of ewes)

Small

(20–99)

Medium 

(100–499)

Large (500

or more)

All 

operations

ELISA

Operations 142/183

(77.6%)

138/151

(91.4%)

68/74

(91.9%)

348/408

(85.3%)

Animals 481/1,827

(26.3%)

521/1,506

(34.6%)

197/740

(26.6%)

1,199/4,073

(29.4%)

PCR

Operations 165/203

(81.3%)

159/173

(91.9%)

78/78

(100.0%)

401/453

(88.5%)

A lower percentage of operations with small flocks

were PCR positive for M. ovipneumonia compared with

operations with medium or large flocks (table 1). This

finding was true for both the ELISA and PCR tests 

(p<0.01). The percentages of seropositive ewes in small, 

medium, and large flocks were consistent across flock 

sizes. 

All herded range flocks were PCR positive, while 

86.4 percent were ELISA positive (table 2). In herded 

range flocks, 25.9 percent of ewes had antibodies to 

M. ovipneumonia. The percentages of PCR-positive 

flocks in fenced range and pasture managed flocks were

similar to the ELISA seroprevalence. Ewe level 

seroprevalence did not vary by flock type (table 2). 

Table 2. Number and percentage of operations 

and animals PCR and ELISA positive for 

M. ovipneumonia, by flock type

Number (Percent)

Flock Type

Herded 

range

Fenced 

range Pasture Dry lot

ELISA

Operations 38/44

(86.4)

74/86

(86.0)

208/246

(84.5)

28/32

(87.5)

Animals 114/440

(25.9)

238/860

(27.7)

750/2,453

(30.6)

97/320

(30.3)

PCR

Operations 47/47

(100.0)

83/94

(88.3)

237/277

(85.6)

34/35

(97.1)

The mean flock size in PCR-positive operations was 

larger (689 ewes, standard error 85.3) compared with 

the mean flock size for PCR-negative operations 

(103 ewes, standard error 15.0). ELISA-positive 

operations were also larger, on average, than ELISAnegative operations (680 ewes in positive operations 

compared with 375 ewes in negative operations). This 

size difference was true for all regions in the study, with 

the exception of the Central region ELISA results.

Conclusions

The high percentage of PCR- and ELISA-positive 

flocks indicates M. ovipneumonia is a ubiquitous 

organism in U.S. sheep flocks. All herded-range flocks 

were positive for M. ovipneumonia carriage. A higher

percentage of medium and large flocks than small flocks 

tested positive.

Detection of DNA fragments in the nasal cavities of 

ewes indicates carriage and possibly shedding, but not 

necessarily active infection. Factors such as weather, 

movement, crowding, or poor nutrition may affect ewes’ 

ability to respond to M. ovipneumonia exposure. The 

presence of this opportunistic pathogen may be 

important for producers experiencing lamb-growth 

impairment associated with chronic, nonprogressive 

pneumonia or that are experiencing lamb mortality 

associated with bronchopneumonia, which is usually 

associated with underlying M. ovipneumonia infection. 

Producers can reduce the likelihood of disease from 

M. ovipneumonia by avoiding overcrowding, isolating 

newly added sheep and lambs, and improving ventilation 

indoors. Antibiotic treatment may help temporarily, but 

response likely varies depending on the strain of 

M. ovipneumonia involved. 

Further work should be done to describe the on-farm 

ecology of this organism and the factors that contribute 

to shedding of the organism.

United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture
References

Alley MR, Ionas G, Clarke J. 1999. Chronic nonprogressive pneumonia of sheep in New Zealand – a 

review of the role of Mycoplasma ovipneumoniae. New 

Zealand Vet J 47(5):155–160.

Alley MR. 1987. Effects of pneumonia on lamb 

production. Proceedings of the New Zealand Veterinary 

Association Sheep and Beef Cattle Society 17, 163–170.

Clarke, JK, Brown VG, Alley MR. 1974. Isolations and 

identification of mycoplasmas from the respiratory tracts 

of sheep in New Zealand. New Zealand Vet J 47:591–

596.

Niang, M, Rosenbusch RF, Andrews, JJ, Lopez-Virella, 

J, Kaeberle, ML. 1998. Occurrence of autoantibodies to 

cilia in lambs with a ‘coughing syndrome’. Vet Immunol 

Immunopathol 64:191–205.

Niang M, Rosenbusch RF, DeBey MC, Niyo Y, Andrews 

JJ, Kaeberle ML. 1998. Field isolates of Mycoplasma 

ovipneuimoniae exhibit distinct cytopathic effects in 

ovine tracheal organ cultures. Zentralbl Veterinarmed A

45:29–40.

Nicholas R, Aylin R, Loria G. 2008. Ovine mycoplasmal 

infections. Small Ruminant Res 76:92–98.

Nicholas R, Ayling R, McAuliffe L. 2008. Mycoplasma

Diseases of Ruminants: Disease, Diagnosis and Control. 

CABI, Cambridge, MA.

Shahsad W, Ajuwape AT, Rosenbusch RE. 2010. Global 

suppression of mitogen-activated ovine peripheral blood 

mononuclear cells by surface protein activity from 

Mycoplasma ovipneumoniae. Vet Immunol

Immunopathol 136:116–121.

USDA. 2010. Sheep and Lamb Nonpredator Death Loss 

in the United States, 2009. Fort Collins, CO.

591.0511.

USDA. 2012. Sheep 2011 Part I: Reference of Sheep 

Management Practices in the United States, 2011. 

USDA–APHIS–VS–CEAH. Fort Collins, CO

601.0512.

__________________

For more information, contact:

USDA–APHIS–VS–CEAH–NAHMS

NRRC Building B, M.S. 2E7

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000

http://www.aphis.usda.gov/nahms

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United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture